Electronic Structure Characterization of Hydrogen Terminated n-type Silicon Passivated by Benzoquinone-Methanol Solutions

The electrical passivation mechanism of benzoquinone-methanol solutions on silicon has been examined through the study of the silicon surface electronic structure. Surface photovoltage (SPV) measurements using both X-ray photoelectron spectroscopy (XPS) and scanning Kelvin probe microscopy (SKPM) indicate a downward band bending of H-Si and benzoquinone (BQ) and methanol (ME) treated samples. This suggests the creation of an accumulation layer of majority carriers near the surface, with a significant field-effect contribution to the observed surface passivation. The highest SPV values recorded for the ME-Si and BQ-Si samples of about −220 mV are approaching the Fermi level—conduction band crossover. Density functional theory (DFT) calculations show that a dipole is formed upon bonding of BQ radicals on the surface, decreasing the surface electron affinity and work function. Considering the 0.07 eV shift due to the dipole and the 0.17 eV downward band bending, the work function of BQ-Si is found to be 4.08 eV. Both the dipole and downward band bending contribute to the formation of surface electron accumulation, and decrease the minority carrier density of n-Si passivated by BQ.